Hi

I have a 1972 Dodge Charger 318 150HP Motor.

I was looking for a 340 for my charger, but was told by someone that in 1972 the motors were high compression, but that in 1973 they went with low compression motors. I was told that I would be better off punching out this 318 to a 340 or larger since I know it is a good motor and changing the pistons and heads, rather than trying to find a 340 and rebuilding.

Can you punch out a 318 that far. Any thoughts on this would be a great help

Thanks
Rael

 

273,318,340,360 are all the same LA blocks just a different bore and stroke.

 

You might try to find the Direct connection racing manual set Rael, part #P4007933. (The revision '79 yellow cover book is the one you want)
It's an old book and you might have to look around a bit, but it's worth having.
The 340 bore is 0.120" larger than the standard bore on the 318. That's a whole lot........you stand a good chance of boring right through the cylinder wall and into the water jacket by going that big, even if it didn't strike water the cylinders would be too thin to run - they tend to deflect and crack under load when they're too thin.
I seem to recall there were some thick wall truck 318's that could go bigger, but do the homework. None are listed in the racing manuals.
The 340's and 360's have much more in common with each other than they do with the 273 and 318, including a different left side engine mount.
Anything is possible however, and welding up or buying a set of mounts sure isn't the end of the world.
A 318 at .030" over will give you 323 cubic inches - and with some 10.5 to 1 pistons, a cam, a good 4 barrel intake manifold and headers should give you an easy 250 H.P. or more.
There were stock 2 barrel 318's in '69 that were rated at 210 H.P............................. I had one in a '63 Dodge pick up - it went like stink.
You probably wouldn't be dissapointed.............[8D]

 

a 318 has the same stroke as a 340 thats why its a high reving engine it has a smaller stroke as we all know the 360 has a 4.000 bore the 340 used a 4.040bore so take a 360 punch it .040 over and put in a 318 crank a 273 a 318 and 340 all used the same crank to get the 3.310 stroke

 

1971 was the last year for the best engines and saw the first signs of detuning by lower compression in some engines. 1972 was heavy hit with lower compression in most every engine. The 340 went from 10.4:1 compression in '71 to 8.5:1 compression in '72 and most enginesby '72were around 8.5:1 compression.

Due to the rarity of andhigh dollarvalue of 340's you would be better off getting a 360 and having fun with it.

 

i built a 318 that produces 325hp with a stock 2bbl and exhaust manifolds in my 68 coronet stock car! the same motor with a hi rise intake 4bbl and headers produces around 400 to 450hp depending on the cam you pick. and valve springs are a big part of it as well.
don't run out and buy some exotic bs that doesn't work to start with. i don't knowwhat 318 that wasn't 200hp, a bone stock 273 willput out almost 200hp! with a 2bbl and exhaust manifolds.
this is what i did! i took a 82' 318 out of an old police cruiser and ihad a 1970 ,360 i blew up racing. aawj heads and the 2v intake.exhaust manifolds, and i put allthat on that 318 with a comp cams extreme energy cam, comp cams varible duration lifters and comp cams push rods,
7.3 liter valve springs. that engine produces 325 hp. i hadmy car dyno'd so i do know what kind of
horse power i'm building and at what rpm!

jhemi

 

I too would "warm over" the 318. When tweaked w/ 4rl, some cam, headers they wake up nicely and much less expensive than the other route. Had a buddy w/ a '74 Dart Sport 318, 2 brl, 3 spd, headers and some gears and that thing surprised many Camaros of the day!

 

hey guys,
i think the 318 is a good engine. back in the day the 273 was the format for the 318,340,and the 360.the 360 is a big small block, it has a long stroke of a big block and it will bolt up to a small block tranny caution: if you put a 360 in the place of a 318 change the flywheel and or the torque converterthey are very different #1 the 318 is internally balanced and the 360 is eternally balanced.my bible says you can take a 318 and bore it .040 over and you have a 340. but why?
take your 318 have some fun with it!

jhemi

 

if it ain't mopar it ain't no car!!!!

jhemi

 

If youre looking for displacement you could always stroke that 318. SCAT makes an awesome 3.58 stroke crank (360 crank) to fit in the 273/318/340. Coupled together with a .030 overbore makes a powerhouse 349 that keeps the dish pistons so its a bit cheaper. Flat tops are a craze, but with 66cc heads youd be looking at 11.8:1 CR. If you got the old 72cc heads tho go for the flattops (10.9:1). Also that SCAT crank is super-light so with a balanced assembly and some valvetrain work you can still get some good revs out of it.